We were privileged yesterday to meet with Robert Fan, Vice President and General Manager of Silicon Motion to discuss their latest SSD controller, the SM2256, which features support for TLC NAND. Historically, TLC NAND has had a reputation of having low endurance and reliability, and hence was not suitable for use in solid state storage devices. Fast-forward to today, and we are seeing new technology and software/firmware tools that are able to increase both the reliability and endurance of TLC NAND, now making it a viable alternative to the more expensive MLC NAND for use in certain SSDs.

The SM2256 supports a wide variety of NAND chips, including ONFI 3.0, toggle 2.0 and asynchronous NAND. It also supports the latest process geometries, including 1x, 1y, and 1z NAND from all major NAND suppliers, and includes 3D NAND. The SM2256 is a 4-channel controller, yet offers performance that rivals that of 8-channel controllers. It supports up to 32 NAND devices, which gives it the capability to support up to 1TB of flash storage. The SM2256 also features a 16-bit wide DRAM interface at DDR3/DDR3L speeds.

As an OEM solution, the SM2256 offers controller and firmware from a single source, simplifying its usage. The firmware is both customizable and upgradeable. The SM2256 supports both device sleep mode (DevSleep) and PHY sleep mode (CFast PHYSLP), as well as TRIM functions. It also features S.M.A.R.T. drive performance and health monitoring attributes.

In the above image, we see a trio of engineering samples that are utilizing the Silicon Motion SM2256 with various NAND configurations. In the close-up shot below, we see the SM2256 residing on the PCB of a 512GB SSD utilizing 19nm TLC NAND and a 512MB DDR3 DRAM chip from Hynix.

The SM2256 also features Silicon Motion’s proprietary NANDXtend technology, which utilizes three levels of error correction and data protection to effectively triple the program/erase cycle count for TLC NAND. Combined with global wear-leveling algorithms, the lifespan of an SSD utilizing the SM2256 is significantly extended. It also features real-time AES256 encryption, as well as being TCG Opal compliant.

Performance of the SM2256 is augmented by utilizing an SLC cache. Real world performance numbers from qualifying OEMs put sequential read speeds at a range from 514MB/s to 545MB/s. Qualifying sequential writes range from 458MB/s to 477MB/s. Random 4K read speeds are averaging 97,000 IOPS, with random 4K write speeds averaging around 40,000 IOPS. The screenshot below shows similar results.

Silicon Motion has enjoyed widespread adoption of their previous SM2246 controller, which is being utilized by over 30 OEMs as shown in the graphic below. For additional information click on “SM2256” in the selection guide here at Silicon Motion’s website. This will take you to the product page for the SM2256.

Silcion Motion is currently qualifying the SM2256 with quite a number of OEMs. Availability is aniticpated for late Q1 of 2015. Watch for further developments as we begin our CES 2015 private meetings and convention hall(s) explorations over the next three days. Don’t touch that dial!